title: NMR identification of a partial helical conformation for bombesin in solution.
abstract: The conformation of bombesin in trifluoroethanol/water mixtures has been studied using 1H-NMR spectroscopy. By a combination of two-dimensional 1H-NMR techniques and measurement of vicinal NH-alpha-CH spin-spin coupling constants, the secondary structure of the molecule has been determined. Bombesin adopts a helical structure in the region from Asn-6 to Met-14 with the remaining N-terminal portion existing as a more extended structure. The structure is very similar to that proposed from Fourier-transform infrared spectroscopic measurements for bombesin inserted into lipid bilayers [D. Erne & R. Schwyzer (1987) Biochemistry 26, 6316-6319]. The absence of a hydrogen bond between the sidechains of Trp-8 and His-12 is discussed in terms of the ionization state of His-12. Stabilisation of the helix results when His-12 is in the ionized state.
authors.affiliation: Department of Chemistry, University of Wollongong, Australia.
authors.forename: J A
authors.initials: JA
authors.lastname: Carver
authors.forename: J G
authors.initials: JG
authors.lastname: Collins
mesh_terms: D001839:Bombesin; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D012996:Solutions; D014270:Trifluoroethanol; D014867:Water
chemical_list: D012996:Solutions; D014867:Water; D014270:Trifluoroethanol; D001839:Bombesin